Control system for fabric drying apparatus



Aug. 3, 1965 T. R. SMITH 3,197,884

CONTROL SYSTEM FOR FABRIC DRYING APPARATUS Filed March 20. 1961 2 Sheets-Sheet l Aug. 3, 1965 T. R. SMITH CONTROL SYSTEM FOR FABRIC DRYING APPARATUS 2 Sheets-Sheet 2 Filed March 20, 1961 XOOO UUD

XXXOO XXXQO OXOQ OOOQXO Ea msammm rm 6 6 mzmtuzi United States Patent 3,197,884 CONTROL SYSTEM FOR FABRhC DRYENG APPARATUS Thomas R. Smith, Newton, Iowa, assignor to The Maytag Company, Newton, Iowa, a corporation of Delaware Filed Mar. 20, 1961, Ser. No. 96,855

6 Claims. Cl. 54-45) The present application is a continuation-in-part of application Serial No. 22,323, filed April 14, 1960, now abandoned, assigned to the same assignee as the instant application.

This invention relates to a control system in a machine for drying fabrics, and more particularly, to a system for automatically controlling termination of drying and auxiliary operations.

It is an object of the present invention to provide a control system for a fabric treating machine which controls [a drying and auxiliary operation. It is a further object of the invention to employ at least a portion of the control for terminating both the drying and auxiliary operations. Further objects and advantages of this invention will become evident as the description proceeds and from an examination of the accompanying drawings which illustrate several embodiments of the invention and in which similar numerals refer to similar parts throughout the several views.

In the drawings:

FIGURE 1 is a View in vertical section, part-1y broken away, illustrating a drier which incorporates the control system of the invention;

FIGURE 2 is a bottom view of one of the baflies shown in the drum of the drier in FIGURE 1, illustrating the location of the electrodes;

FIGURE 3 is a schematic diagram of a preferred circuit employing the principles of the control system of the present invention;

FIGURES 4 and 5 are tables illustrating the positions of the switch contacts of switch 95 in FIGURE 3 for various selected settings.

Briefly described, the invention relates to a fabric treating machine having a drying operation and auxiliary operation. Itis concerned with a control system in which conductors, electrodes, or probes, directly contact fabrics being dried, and control termination of the drying operationafter their electrical resistance, or conductivity, dependent upon their condition of dryness, exceeds a predetermined value for a predetermined time, as determined by a capacitance-resistance circuit, following which at least a portion of the capitance-resistance circuit is used to control the auxiliary operation.

In FIGURE 1 of the accompanying drawings is shown a clothes drier having a base frame .10 which serves as a support for upstanding channel base members 11 and 12 which together with cross piece 14 support the hollow blower housing casting 17. Housing 17 includes a tubular portion 21, a divider wall 20 having a rearwardly flared inner portion defining an intake into an impeller chamber, and radially directed longitudinal webs 22 which converge toward each other to provide a retainer member 23. A passageway 26 is located between the tubular portion 21 and the bearing retainer member 23 which transverses the supporting webs 22.

Journalled within member 23 is a revoluble drum drive shaft 31 which projects from both ends of the housing 17. Aflixed to drum drive shaft 31 at the rear of the cabinet is a large pulley 33 which is driven by motor 354 through motor pulley 36, main drive belt 37, a speed reduction system (not shown) and belt 40.

The opposite or forward end of the drum drive shaft 31 is rigidly connected to the drum spider member 46 which has radiating spokes 51 that support rim 52. A heat resistant sealing member 54 encircles the front periphery of blower housing 17 and the circular shoulder 55 located on the rear portion of drum spider 46.

A horizontally mounted tumbling drum 60 has a rear wall 61 which is secured to rim 52 for support and rotation by shaft 31. Rear drum wall 61 is imperforate except for a central exhaust opening 62.

The periphery of rear wall 61 is flanged to form a supporting shoulder for the imperforate cylindrical side wall 65 which carries the clothes elevating vanes 66 for tumbling clothing within drum 60 during rotation of the latter member. Cylindrical side wall 65 is connected to the front drum wall 67.

Front wall 67 has a centrally located access opening 68 and acircular perforate portion 69 located concentrically to access opening 68. This perforate portion 69, formed by several concentric rows of holes, serves as the air intake into drum 60.

The cabinet 70 which is fastened to base frame 10 and which encloses the entire drying mechanism has an access opening 71 aligned to drum access opening 68 thereby allowing both of openings 68 and 71 to receive the door gasket 72. The door 73 is hinged and forms an airtight seal with gasket 72.

Fastened to cabinet 70 is the shroud or cowling member 74. Located between shroud 74 and the front drum wall 67 is an open coil electric heating element 75 which extends completely around the inside of cowling member 74 to raise the temperature of air passing through perforate portion 69 in the front drum wall 67. It will be understood that a gas heater may be used in place of the electrical element.

Air flow into drum 60 through the perforate area 69 and into the blower housing 17 is produced by rotation of the revoluble impeller member 76 located in blower housing 17. Fan pulley 77 is connected to the driving motor 34 by main drive belt 37. The blower housing casting 17 supports a cycling thermostat 78 which isconnected in series with the heating element 75 in order to maintain the interior of drum 60 at the proper selected drying temperature. In practice, this switch is set to open at approximately 135.

Also connected in series with the heating element 75 is the high limit switch 79 which is mounted on an upper part of shroud member 74 so a to disconnect heating element 75 from its source of power in case the temperature near the front of the drum should rise above a predetermined selected temperature during the operation of the clothes drier, for instance, in the event of reduced air flow through drum 60.

In order to measure the electrical conductivity or resistance for determining the condition of dryness of the fabrics, electrodes or probes 80, 81 are mounted within the drum 60. In the form shown, the electrodes are spirally Wound about each of the drum baffles 66 to provide a maximum amount of contacting or probing surfaces exposed to the fabrics placed within the drum.

As best illustrated in FIGURE 2, the electrodes are preferably set in recesses or grooves in the bafiles to prevent shorting therebetween by metallic objects sometimes attached to the fabrics, for example, metal buttons, clips, buckles, and the like. It will be realized that different forms of electrodes, or probes, may be used, although the type disclosed herein is preferred.

Electrical energy is supplied to electrode by lead 84 that is connected to brush 85 which engages the stationary slip ring 86 while the drum 60 is rotating. The slip ring 86 may be supported on an electrically insulative band 87 mounted on housing 17. Slip ring 86 is in turn connected to a lead 90 which runs to the control unit 92.

upper portion of the cabinet.

drying operation. denser 110, gaseous discharge tube 111, light responsive a e'D Electrode 81 may also be supplied with electrical energy of the opposite polarity to electrode 30 by lead 83 that may be connected to a similar arrangement of brushes and slip rings. It is preferred, however, to ground electrode 81'to the rotatable drum 60, so that it is supplied by current from lead 91 which is also grounded to the framework of the drier.

The automatic control unit 92 may be secured to the Leads 90, 91 enter the control unit and are connected to the control circuit to be described hereinafter.

It will be noted that the baflles 56 are formed of electrically non-conductive material in order to insulate the electrodes. However, the electrodes are electrically shorted by contacting the wet fabrics during tumbling. Ordinarily, a plurality of bafiies 66 are mounted Within the drum 60, each of which is provided with electrodes -which may be selected by manual operation of a button (not shown) by the operator. The button is mechanically linked (not shown) to the switch 95, so that by depression of a single button (not shown), marked for any of the ,foregoing settings, the switch contacts a through 1' are connected or disconnected as indicated by FIGURE 4 according to the legend of FIGURE 5. It should be clear that the switching arrangement may include other selections, as well as those indicated.

The drier drive motor is energized by a conventional 3-wire system. The circuit is from power line L contacts g-h of switch 95, line 106, to one side of the motor 34. The other side of the motor 34 is connected to power line N. The motor 34 contains a centrifugal switch having a contact 101 which is closed when the motor reaches .a predetermined speed to connect power line L to one side of the heater 75.

The heater is connected to 220 volts A.C. between L and L by a circuit from L line 102, contacts n1-n of switch 95, line 103, thermostats 78 and '79 to one side I of the heater 75. The other side of the heater 75 is connected to L through centrifugal switch 101.

The control circuit includes a sensing circuit for determining when the clothes are dry, or at a predetermined dampness, in order to initiate termination of the The sensing circuit includes the conelement 112, and relay 113. The relay 113 (shown de- .energized) has switch contacts 114, 115, 116 and 117.

The sensing circuit and its operation is more fully described in application Serial No. 22,323, filed April 14,

1960, referred to hereinabove. The condenser 110 is charged by a circuit from power line L contacts g-h, line 106, line 107, relay switch contact 116, line 129, line 130, through half-wave rectifier 120, and resistor 121 to one side of the condenser 110. The other side of the condenser is connected to power line N through resistor 122. ,The resistors 121, 122 and condenser 110 are charged over a time period in accordance with well-known capacitance- .resistance principles. The gaseous discharge tube 111 is connected in parallel to condenser 110 so that when the voltage charge on the condenser reaches a predetermined value the tube 111 is fired. The firing of the gaseous tube tact 114- (in the position illustrated when the relay 113 is de-energized), relay 113 to power line N.

When the relay 113 is operated, switch contact 114, is opened disconnecting the circuit to the light responsive element 112. Switch contact 115 is closed to complete a circuit to energize solenoid A. Switch contact 116 is opened to disconnect the condenser from the power line. The contact 117 is closed to complete a holding circuit to maintain the relay 113 energized.

The solenoid A is energized upon closing of switch contact either by a circuit from power line L contacts mn, line 103, thermostat 78, line 118, switch contact 115, line 126, line 127, contacts a-b to one side of the solenoid A or by a circuit from power line L contacts qr, line 90, line 118, switch contact 115, line 126, line 127, contacts ab to one side of the solenoid A. The other side of the solenoid is connected to power line N.

The holding circuit for the relay 113 upon closing of relay switch contact 117 is from power line L contacts g-h, line 106, line 128, contacts c-d, line 129, relay switch contact 117 to one side of relay 113. The other side of relay 113 is connected to power line N.

Referring now to FIGURES 3, 4 and 5 of the drawing, when a regular dry setting has been selected, the switch contacts a through r of switch 95 are operated as indicated by the table in FIGURE 4. Thus, contacts a-b, cd, g-h, and in through r are closed, switch contacts e-f and k-l remain open, and contacts i-j are momentarily closed. 7

When contacts ab and q-r of switch 95 are closed, solenoid A is connected to a circuit in order to energize solenoid A when the relay 113 is operated. Contacts ab and q-r are in series with contacts 115 of relay 113 as previously described.

When contacts c-d of switch 95 are closed, the holding circuit for relay 113 is in a position for maintaining the relay energized. When the solenoid A is operated, switch contacts c-d open and the relay holdingcircuit is broken to return the relay to de-energized position. Contacts c-d are in series with the holding circuit through relay contact 117 of relay 113 as described hereinabove.

When contacts g-h of switch 95 are closed, the drier drive motor 34 and the sensing circuit are energized. The circuit is from power line L through contacts g-h to line 106. The drive motor 34 is connected on one side to line 106 and on the other side to power line N. Line 106 is connected to line for supplying power to the light responsive element 112 and relay 113, so that when the gaseous discharge tube 111 fires the relay 113 will .be operated. Line 106 is connected to line 107 for supplying power to the half-wave rectifier 120 through relay switch contact 116 and line in order to apply direct current to the condenser 110, as more fully explained hereinabove.

When contacts i of switch 95 are momentarily closed, the condenser 110 is momentarily shorted to discharge any remaining voltage. By shorting the condenser at the start of an operation, the time period determined by the capacitance-resistance circuit will be the same for each operation. The shorting circuit is from ground through contacts i to line 132 to one side of the condenser 110. The other side of the condenser is connected to ground through line 91.

When contacts m-n of switch 95 are closed, the heater 75 of the drier will be energized, upon closing of centrifugal switch 101, as explained hereinabove. It will be noted that the thermostat 78 is normally in the position as shown by the full lines in FIGURE 3. However, when the temperature rises above approximately F. the thermostat moves to open the circuit to the heater 75 and completes the circuit to line 118, as shown by the dotted line position.

When contacts 0-p of switch 95 are closed, the electrodes 80 are connected across the condenser 110, as previously described. As long as the electrodes are contacted by wet fabrics they discharge the charge on the condenser 110. However, as the fabrics become dry, the rate of discharge between the electrodes 80, 81 decreases, so that the charge on the condenser 111) rises until a point is reached at which the gaseous discharge tube 111 is fired.

When a Wash & Wear setting has been selected, the same contacts of switch 95 are closed as for Regular Dry, except q-r. During the Wash & Wear cycle, q-r remains open so that the 115 volts is not placed on line 118 until the thermostat 7 8 has moved to the dotted line position, after the drier temperature has been raised to above 155 F. This means that the solenoid A is not energized until the thermostat 78 has been moved to the dotted line position to place 115 volts on line 118. Wash and wear fabrics need to be dried at higher temperatures in order to remove wrinkles. By placing the energization of solenoid A under the control of thermostat 78, the temperature condition of the drier for wash and wear fabrics is controlled to delay termination of the drying operation until the proper temperature is achieved.

When a Damp Dry setting has been selected, the contacts of switch 95 are identical to that of the Regular Dry setting, except that contacts k-l are additionally closed. Contacts k-l place an additional resistor 134 in parallel to resistor 121. This reduces the effective resistance of the capacitance-resistance circuit. As a result condenser 110 is charged at a faster rate, and the sensing circuit operates to initiate termination of the drying operation while the fabrics within the drier are still damp. In this way, the drying operation is terminated so that the operator can remove the damp fabrics for ironing.

When a Air Fluff setting has been selected, the contacts of switch 95 are operated as for the Regular Dry setting, except contacts m-n and -p remain open. The Air Fluff setting is merely a timed period for tumbling the clothes without the heater energized. Therefore, the contacts m-n of the heater circuit remain open. The circuit employing the electrodes 80, 81 also remains open through contacts o-p, since the condition of fabrics is not utilized in determining the duration of the operation.

It is often desirable to perform an auxiliary operation following the drying operation. Thus, by way of example, it may be desired to tumble the fabrics for a predetermined period after the heater has been de-energized for cooling. Other auxiliary operations may be utilized. The present invention employs the capacitance-resistance circuit for timing the auxiliary operation.

After the fabrics have been dried to a predetermined moisture content, as determined by the sensing circuit containing probes 8t), 81, the condenser is charged to a point which fires the gaseous discharge tube 111. This reduces the resistance of light responsive element 112 to operate relay 113. When relay 113 is operated, the solenoid A is closed. As indicated by the table of FIGURE 4, when solenoid A is energized, it opens all of the switch contacts of switch 95 except e-f, g-h, and q-r.

The energization of solenoid A initiates the auxiliary operation, and terminates the drying operation by disconnecting heater 75. Contacts e-f are closed during the auxiliary operation to place the solenoid B in series with relay switch contact 115. The circuit is from relay switch contact 115, line 126, line 140, contacts e-f, line 131, to one side of solenoid B. The other side of solenoid B is connected to power line N. It will be realized that when relay switch contact 115 is closed, 115 volts is applied from line 118, in order to energize the solenoid B.

Contacts c-d of switch 95 are opened during the auxiliary operation upon the energization of solenoid A in order to break the holding circuit of relay 113. Relay 113 is deenergized and the relay switch contacts assume their normal positions, as shown in FIGURE 3.

As previously explained, switch contacts g-h of switch 95 energize the drier drive motor 34 and also the circuit which energizes condenser 110 through resistors 121, 122, and half-wave rectifier 120. The relay 113 being deenergized at the beginning of the auxiliary operation, the condenser is again charged over a time period determined by capacitance-resistance principles until the gaseous discharge tube 111 fires to illuminate light responsive element 112 and operate the relay 113. In this way, the capacitance-resistance circuit is utilized to time the auxiliary operation.

Contacts 0-p of switch are opened during the auxiliary operation so as to remove the electrodes or probes 3d,

81 from the circuit across the condenser 110. Thus, after the solenoid A is energized, the capacitance-resistance circuit, including condenser 110, operates in accordance with well known principles to time a predetermined period of operation, Without reference to the dryness of the fabrics since the circuit to the probes 8t), 81 is disconnected. The capacitance-resistance circuit is employed during the drying operation to determine the con dition of the fabrics, and to initiate the termination of the drying operation. However, following the drying operation, when the auxiliary operation is started by energizing solenoid A, the capacitance-resistance circuit is utilized to measure a predetermined time period for determining the duration of the auxiliary operation.

When the relay 113 fires after the auxiliary operation time period, as determined by the capacitance-resistance circuit of condenser 110, relay switch contact is closed, and solenoid B is energized. When the solenoid B is energized, all of the switch contacts a-r are discon' nected as indicated by FIGURE 4, in order to terminate the entire operation.

From the foregoing, it is believed that operation of the device is apparent. The operator opens the door 73 of the drier and inserts fabrics in the drum 60. The operator sets the button (not shown) 'at the desired selection, for example, Regular Dry position. The drive motor 34 is then energized to rotate the drum 60 to tumblethe clothes by bafile 66. After a certain rotational speed is achieved by the drive motor 34, switch 101 is centrifugally operated to close the circuit to heater 75.

As long as the fabrics within the drum remain wet, or suficiently damp to effectively discharge the condenser 110 at a rate faster than the charge through rectifier 120, the drying operation continues. The condenser 110 is charged by the half-wave rectifier through resistors 121, 122, and is discharged by the damp fabrics shorting the condenser 110 through electrodes 80, 81. When the moisture is removed from the fabrics to a predetermined amount and maintained at a predetermined dryness over a predetermined time period determined by the capacitance-resistance circuit, the charge on the condenser 110 accumulates. When the accumulated charge on the condenser 110 reaches a predetermined amount over a predetermined period of time of suflicient duration for all the clothes within the drum to contact the electrodes 80, 81 during tumbling, termination of the dry ing operation will be initiated. Thus, if a damp fabric has been trapped by dry fabrics, as the drum continues to rotate, the damp piece will eventually contact the electrodes 80, 81 and discharge the condenser 110 to prevent termination of the drying operation. On the other hand if the pieces are all dry, termination of the drying operation will be initiated by the sensing circuit through the firing of the gaseous discharge tube 111 by the charge accumulated on the condenser 110. When the gaseous discharge tube 111 fires, the light responsive element 112 is illuminated, and its resistance reduced, to complete the circuit to relay 113. When the relay 113 is energized it is maintained energized by the holding circuit through relay contact 117. Energization of the relay 113 also operates the solenoid A through the relay switch contact 115. When solenoid A is energized, it operates to discontinue the drying operation and initiate the auxiliary operation.

Upon energization or operation of the solenoid A the auxiliary operation is initiated and continues for a time is again fired to illumine the light responsive element 112,

and operate relay 113. When this occurs the solenoid B is energized through a circuit including contacts e-f of switch 95 to discontinue all of the functions, including the auxiliary operation, and stop the machine.

By way of example, and not as any limitation on the invention, the gaseous discharge tube 111 is designed to fire at approximately 72 volts. The capacitanceresistance circuit is designed so that it takes about 7 to 8 minutes to charge the capacitance to an amount suificient to fire the tube 111, apart from the discharge time through electrodes 80, 81. The drying time period, therefore, will be greater than 7 to 8 minutes duration. The auxiliary operation will be 7 to 8 minutes, or less depending on the residual charge of condenser 110 following the rying period.

In the drawings and specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed, these are used in a generic and descriptive sense only, and not for purposes of limitation. Changes in form and the proportion of parts, as well as the substitution of equivalents are contemplated, as circumstances may suggest or render expedient, without departing from the spirit or scope of this invention as futher defined in the following claims.

I claim:

1. In a fabric conditioning machine having a chamber for containing fabrics and heating means for drying fabrics in said chamber, means for operating said machine through a first operation in which said heating means is energized, means for operating said machine through an auxiliary operation in which said heating means is deenergized, and circuit means including charging resistor means and condenser means for timing at least a portion of said auxiliary operation.

2. In a fabric conditioning machine having a chamher for containing fabrics and heating means for dry ing fabrics in said chamber during a first operation, means for operating said machine through an auxiliary operation following said first operation, and circuit means including charging resistor means and charging capacitor means for timing at least a portion of said auxiliary operation.

3. In a fabric conditioning machine having a drying operation and at least one sequential operation comprising, means for initiating said sequential operation, timing circuit means having charging capacitor means for regulating at least a portion of the period of at least one of said sequential operations, and means for charging said capacitor means over a timed period after initiating said sequential operation.

4. In a fabric conditioning machine having heating means for drying articles, means for initiating a first operation in which said heating means is energized for a 8 time period under the control of a circuit containing resistor means and condenser means in series, means for initiating a second operation in which said heating means is deenergized, and means for timing at least a portion of said second operation under the control of said resistor means and condenser means.

5. In a fabric conditioning machine having a chamber for containing fabrics and operable through a plurality of selectable operations including a drying operation and an auxiliary operation comprising, first selectable means for initiating said drying operation, first termination means for automatically initiating termination of said drying operation in response to a predetermined degree of dryness of the fabrics, second selectable means for initiating said auxiliary operation, means for substituting a second termination means in place of said first termination means for said auxiliary operation, timing means including capacitance means for maintaining the duration of said auxiliary operation over a fixed period, and means for gradually charging said capacitance means to a predetermined charge, said second termination means being responsive to said predetermined charge on said capacitance means for terminating said auxiliary operation.

6. In a fabric conditioning machine having a chamber for containing fabrics and operable through a plurality of operations including a drying operation and an auxiliary operation comprising, first means for initiating said drying operation, first termination means for automatically initiating termination of said drying operation in response to a predetermined degree of dryness of the fabrics including capacitance means, second means for initiating said auxiliary operation, means for substituting a second termination means in place of said first termination means for said auxiliary operation, timing means including said capacitance means for maintaining the duration of said auxiliary operation over a timed period of predetermined length, and means for gradually charging said capacitance means to a predetermined charge, said second termination means being responsive to said predetermined charge on said capacitance means for terminating said auxiliary operation.

References Cited by the Examiner UNITED STATES PATENTS 1,875,359 9/32 Suits 324 2,045,381 6/36 Elberty 324-65 2,807,889 10/57 Dunkelman 34-45 2,812,491 11/57 Figlio 324-45 2,838,719 6/58 Chitty 317-124 3,021,605 2/62 Anderson 34-45 3,044,181 7/62 Berenbaum 34--45 OTHER REFERENCES Electronics, Maytag Electric Dryers, copyrighted 1960, 12 pages.

NORMAN YUDKOFF, Primary Examiner. 

3. IN A FABRIC CONDITIONING MACHINE HAVING A DRYING OPERATING AND AT LEAST ONE SEQUENTIAL OPERATION COMPRISING, MEANS FOR INITIATING SAID SEQUENTIAL OPERATION, TIMING CIRCUIT MEANS HAVING CHARGING CAPACITOR MEANS FOR REGULATING AT LEAST A PORTION OF THE PERIOD OF AT LEAST ONE OF SAID SEQUENTIAL OPERATIONS, AND MEANS FOR CHARGING SAID CAPACITOR MEANS OVER A TIMED PERIOD AFTER INITIATING SAID SEQUENTIAL OPERATION. 